Recently, with the trend of high speed digitalized communication, high frequency electrical products, computer hardware and software adapted for high speed signals and integrated circuits have developed rapidly. Therefore, the demands for operation frequencies and frequency bands of signals are increasing. Moreover, the increase in the transmission speed of signals and the miniaturization of interconnected products such as connectors, cables or printed circuit boards have resulted in the increased layout densities of circuits. As a result, problems regarding signal transmissions arise, such as signal integrity, electromagnetic interference, electromagnetic compatibility or power integrity.